It's totally normal for a breastfed baby to not poop but 1x a week at this age. They absorb all of the breastmilk and there is no waste. I would not use a thermometer to make her poop. You could inadvertantly perforate her colon that way. Keep an close eye on her wet diapers, but don't worry too much about the dirty ones. She will poop when she needs to. As long as she is exclusively breastfed, constipation is very rare.